In the field of aircraft engine technology, it is well known that extremely hot fluids and combusting fuel mixtures are directed to flow through varying types of conduits ranging from tubes to augmentors, or after-burner sections of gas turbine engines. As disclosed in U.S. Pat. No. 5,385,015 that issued on Jan. 31, 1995 to Clements et al., which Patent is owned by the owner of all rights in the present disclosure, a pilot assembly is utilized to direct flow of flames through flame passages into an augmentor of a gas turbine engine. The flame passages dispense flames into a combustion section of the augmentor through openings that define a circumferential disposition around a tail cone within the augmentor. A pilot combustor is located within the tail cone, and flames are directed from within the cone to the openings around the tail cone.
The hot gases or flames from the flame passages of the pilot are utilized to efficiently ignite fuel within a combustion chamber of the augmentor when the fuel is injected into the combustion chamber through struts or vanes passing between the tail cone and an outer wall of the augmentor. The openings of the flame passages are defined immediately downstream from the fuel dispensing struts and the flames thereby serve to propagate an efficient combustion of the fuel within the augmentor.
The flame passages of the pilot assembly may be formed by metallic tubes that direct flow of hot gases or flames from the pilot combustor to outlets defined around the tail cone within the augmentor. It has been found that such flame tubes are subject to extraordinary mechanical and thermal stresses as the augmentor is used to substantially enhance the thrust of the gas turbine engine, frequently propelling combustion products at supersonic speeds.
Many efforts have been undertaken to produce fluid conduits that provide for limited movement within the conduit to compensate for axial, rotational and angular stresses. For example, published European Patent Application No. EP 0919774 A3 published on Jun. 2, 1999 shows a “flame tube interconnector” that discloses a joint providing limited movement. The joint includes a first transfer tube having a seat that mates with a spherical or conical seat of a second transfer tube. A spring is included within one of the tubes to draw the two tubes into contact with each other, and exterior flanges include complex throughbores for flexibly bolting the tubes together. While providing for limited axial, radial and rotational motion at the joint, this disclosure exposes the spring to rapid wear by being within the tubes, and the bolting mechanism requires complicated manufacture and installation complexities.
More recently, U.S. Pat. No. 6,709,023 that issued on Mar. 23, 2004, to French discloses a “flexible slide joint” that provides for limited motion in a fluid conduit. French shows first and second tube members secured together by a sliding sealing sleeve member that houses an axially compressible element. One of the two members defines a spherical end portion that abuts an interior slide surface of the sealing sleeve member to provide the limited motion. Like Clements et al., the French disclosure requires complex manufacture, assembly and installation of many separate parts that utilize intricate components to secure the many parts as a single tube.
Therefore, there is a need for a tube having a joint that provides for limited angular, rotational and axial movement between portions of the tube while tolerating flow through the tube of extremely hot fluids and experiencing severe mechanical duress associated with supersonic gas turbine engines.